The present invention relates to zinc based bioceramics, and more particularly, to zinc based ceramic surgical cements or grouts and in vivo implants.
Ceramic materials which are useful as drug delivery devices and as hard tissue substitutes in orthopaedic, dental and maxillofacial surgeries include hydroxyapatites, tricalcium phosphates (TCP) and partially resorbable alumino-calcium oxide-phosphorus pentoxide (ALCAP) ceramics. U.S. Pat. Nos. 4,097,935 to Jarcho; 4,149,893 to Aoki et al.; and 4,330,514 and 4,548,959 to Nagai et al. disclose hydroxyapatite ceramics. U.S. Pat. No. 4,192,021 to Deibig et al. discloses calcium phosphates.
U.S. Pat. No. 4,218,255 to Bajpai et al. and Graves, G. A. et al., "Resorbable Ceramic Implants," J. Biomed. Mater. Res. Symp. 2(part I): 91, 1972, disclose ALCAP ceramics. These ceramics are obtained by mixing calcium oxide, aluminum oxide and phosphorus pentoxide in weight ratios of about 35-40% CaO, about 45-55% Al.sub.2 O.sub.3 and about 10-20% P.sub.2 O.sub.5 ; powdering the mixture and calcining. A typical ALCAP ceramic is prepared from a 38:50:12 by weight mixture of calcium oxide, aluminum oxide and phosphorus pentoxide which is calcined at 2400.degree. F. for twelve hours and ground.
U.S. Pat. No. 4,376,168 to Takami et al. relates to sintered calcium phosphate ceramics which are useful as replacements for bones or teeth. In one embodiment, the ceramic is prepared using a frit comprising P.sub.2 O.sub.5 and one or more metal oxides selected from the group consisting of BaO, CaO, MgO, ZnO, Na.sub.2 O, and K.sub.2 O. About 0.5 to 15% of the frit is admixed with a calcium phosphate starting material such as apatite. The compacted mass of the resultant mixture is then sintered. In Table 5, frit example C comprises P.sub.2 O.sub.5, CaO, and ZnO (47:44:9 mol ratio; 68:25:7 wt. ratio).
ALCAP ceramics are advantageous because they are resorbable and stronger than apatite and TCP. However, while there is no evidence that ALCAP ceramics are toxic, aluminum has been implicated in neural and bone disorders and this has cast a shadow on the use of ALCAP ceramics in humans. Thus, a need exists for a resorbable aluminum-free ceramic useful in dental and orthopaedic applications.